This invention relates to a semiconductor nonvolatile memory, and particularly to a method of writing data into and erasing it from an electrically data-reloadable semiconductor nonvolatile memory.
As electrically data-reloadable ROMs (Read Only Memory), there has heretofore been proposed various flash EEPROMs (Electrical Erasable and Programmable ROM) memory cells.
For example, a sidewall type flash EEPROM cell has been described in "IEDM 1989 P. 603 to 606 `A New Flash-Erase EEPROM CELL With a Side Nail Select-Gate on its Source Side` K. Naruke et al."
In this type of sidewall type flash EEPROM cell, the writing of data therein effected by injecting hot electrons thereof into a floating gate.
In this case an energy of 3.1 eV or higher is required to write the data in the sidewall type flash EEPROM cell in view of the structure of the sidewall type flash EEPROM cell to be described later.
Further, when the data is written into the cell under such high energy, the number of times in which the data is rewritten or reloaded reaches several thousands or so.